Problem: $\log_{3}81 = {?}$
Explanation: If $\log_{b}x=y$ , then $b^y=x$ First, try to write $81$ , the number we are taking the logarithm of, as a power of $3$ , the base of the logarithm. $81$ can be expressed as $3\times3\times3\times3$ $81$ can be expressed as $3^4$ $3^4=81$, so $\log_{3}81=4$.